Changes in acetabular orientation during total hip arthroplasty.

Area of Science:

• Orthopedic Surgery
• Radiology
• Biomedical Engineering

Background:

• Pelvic sagittal alignment is crucial for accurate acetabular component placement in total hip arthroplasty (THA).
• Variations in patient positioning during THA can alter pelvic alignment, potentially leading to component malpositioning.
• Understanding these dynamic changes is essential for optimizing surgical outcomes.

Purpose of the Study:

• To quantify changes in pelvic sagittal alignment during and after THA performed in the lateral decubitus position.
• To assess the impact of these alignment shifts on the perceived position of the acetabular component.
• To evaluate the clinical significance of altered pelvic alignment on acetabular component version.

Main Methods:

• Retrospective analysis of 91 patients undergoing THA.
• Radiographic assessment of pelvic ratio in standing (pre- and post-op), lateral decubitus (intra-op), and supine (post-anesthesia) positions.
• Calculation of pelvic ratio and determination of changes in apparent acetabular component version (>5° considered significant).

Main Results:

• Increased pelvic ratio (anterior tilt) observed intraoperatively in 69.4% of cases during lateral decubitus positioning.
• Postoperative comparison revealed decreased pelvic ratio (posterior tilt) in 44.9% of cases.
• Significant changes (>5°) in apparent acetabular component version occurred in 79.6% of cases intraoperatively and 57.7% postoperatively.

Conclusions:

• Dynamic changes in pelvic sagittal alignment occur throughout the THA procedure.
• Unaccounted pelvic positional shifts can introduce errors in acetabular component placement.
• Intraoperative imaging may be beneficial for achieving appropriate acetabular component positioning.